fix typechecking of mutually recursive bindings. implement monomorphism restriction.
fix typechecking of mutually recursive bindings. implement monomorphism restriction.

darcs-hash:20060214100912-1a7c6-950076ea967aa2679955f2e9d125a60fcab059a7

kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc,kirbyfan64/jhc